Tool/software:
Dear TI experts,
I did WEBENCH simulation of LMR14030SSQDDARQ1 to check phase margin and gain margin, but I cannot find these parameters in the results.
Could you help me to find theorical phase margin and gain margin of LMR14030SSQDDARQ1?
Input voltage : 12V
Output voltage : 5V
Output current : 0.2A
Please check this issue. Thanks.
Best regards,
Chase
Hi Chase,
You can use "Simulate>> Bode plot" to generate the bode plot in WEBENCH. You can find PM and GM from the bode plot.
What is the switching frequency?
regards
Arpita
Dear Arpita,
Thank you for your support.
I simulated board plot and got a result below ;
Customer uses Rt as 14.3Kohm, so switching frequency is about 1.57MHz.
The cursor on the bode plot is closest value to 1.57MHz -> 1.545MHz.
Could you help me more to get phase margin and gain margin?
Best regards,
Chase
Hi Chase,
you can directly read PM and GM from the bode plots generated.
, 
For example, the phase angle at gain cross-over freq ~4.7kHz [when gain touches 0 dB] is the phase margin, PM~55 degrees.
Similarly, the GM is ~37dB at phase crossover frequency [when phase touches 0 degrees].
Using the above example, you can find GM and PM for your design.
For more understanding on GM and PM please refer to Microsoft PowerPoint - Gain Margin and Phase Margin.ppt [Compatibility Mode]
Regards
Arpita
